1. Field of the Invention
This invention is particularly suited for gas sensors with an upstream diffusion barrier whose responsiveness is impaired by structural design or contamination, or which are primarily used in static gas atmospheres.
2. Background Art
When gases or vapors reach the sensor(s) by diffusion through porous bodies, it is known that diffusion barriers with a diffusion gradient are formed that impair gas exchange, for gas diffusion through such barrier is determined by the partial pressure difference.,
Thus small measuring ranges and the required high responsiveness can no longer be achieved using conventional gas sensor arrangements, especially when diffusion barriers exist or in static gas atmospheres.
It is the problem of this invention to improve the dynamic properties of the gases and vapors under the conditions mentioned above. This problem is solved by the characterizing features of claim 1 while advantageous embodiments are the subject of the dependent claims. Claim 8 described an alternative use.
The gas sensor arrangement of the invention in which one or more gas sensors are configured to monitor or measure concentrations of gas, vapor or mixtures in rooms and in which the gas sensors are located behind an upstream diffusion barrier so that their responsiveness is impaired by structural design or contamination and/or the gas atmosphere is static, involves that the sensor(s) are located in, on and/or in front of a duct, i.e. in the flow area of this duct, and that a flow is present in this duct when the sensor(s) are measuring or monitoring. Most preferably, the duct extends from down upwards.
The flow can advantageously be generated by the natural difference in temperature, and/or the duct is artificially heated using a heater.
The invention utilizes the finding from practical measurements that even for small gas concentrations to be measured, signal change in remote measuring heads operating on the diffusion principle is clearly greater when the flow changes from near zero to low than when the flow changes from low to high.
In a preferred embodiment, the duct is a tube with at least one lateral opening, most simply a hole, through which the sensor has gas contact.
This module can easily be integrated in a casing that houses measuring and evaluation equipment. The upper and lower ends of the tube pass through the walls of the casing. The sensor may easily comprise an upstream diffusion body. In addition, this arrangement also allows for using dissipated energy from electronic or electric components inside the casing for heating the duct artificially.